1. Field of the Invention
The present invention relates to a liquid ejection head having a piezoelectric element substrate and a method of manufacturing the same.
2. Description of the Related Art
Liquid ejection heads including a piezoelectric element substrate that contains a piezoelectric material such as PZT (Pb(Zr,Ti)O3: lead zirconate titanate) are known.
Pressure chambers for applying ejection pressure onto ink are formed in a liquid ejection head including a piezoelectric element substrate, and electrodes are arranged respectively on the inner surface and on the outer surface of the lateral wall of each pressure chamber and electrically connected to a head substrate. As a voltage is applied between the electrodes from the head substrate, the lateral wall of the pressure chamber is deformed to change the capacity of the pressure chamber so that ejection pressure is applied to the ink in the pressure chamber and ink droplets are ejected from the ejection port that is held in communication with the pressure chamber.
Japanese Patent Application Laid-Open No. 2008-143167 discloses a harmonica type liquid ejection head. In the harmonica structure of the disclosed liquid ejection head, pressure chambers and apertures are alternately arranged in the direction of arrangement of pressure chambers within the piezoelectric element substrate of the liquid ejection head. Thus, the two lateral walls of a pressure chamber sandwiched between the pressure chambers and the respective apertures can be deformed by electrically driving the piezoelectric element substrate.
Japanese Patent Application Laid-Open No. 2007-168319 discloses a pinholder type liquid ejection head including pressure chambers, and the lateral walls of the pressure chambers located at the ejection port side of the liquid ejection head are independently arranged, whereas the lateral walls of the pressure chambers located at the ink supply port side that is opposite to the ejection port side are linked to each other. With the pinholder structure, four lateral walls at the ejection port side where the lateral walls are independently arranged can be deformed at a time by electrically driving the piezoelectric element substrate so that a greater capacity change can be realized.
However, with a liquid ejection head having a harmonica structure as described in Japanese Patent Application Laid-Open No. 2008-143167, the deformations of the piezoelectric element substrate structurally give rise to crosstalk to a large extent because the pressure chambers are connected throughout the full length of the respective pressure chambers.
With a liquid ejection head having a pinholder structure as described in Japanese Patent Application Laid-Open No. 2007-168319, the deformations of the piezoelectric element substrate structurally give rise to crosstalk to a lesser extent because the pressure chambers are held independent from each other at the drivable part of the respective pressure chambers. However, the linked parts of the lateral walls cannot be driven with this structure. If the drivable parts are to be made longer, the only possible way to do so is to make the independent parts of the pressure chambers longer. Then, the mechanical strength of the pressure chambers is inevitably reduced. Particularly, when ejection ports are to be arranged highly densely, the mechanical strength of the pressure chambers are reduced further because the aspect ratio of the independent parts of the pressure chambers is large.